dlr

[tube10]

is dlr consider a tram system and how it differs from the old trams in terms of operation and signals including power supplies?

[Oracle]

Isn't it actually light rail, as per the Tyneside Metro? That said, both are often lumped in with say Croydon under "trams", although I believe the overall description might be LRT or Light Rapid Transit. The Metro cars were originally designed so that they could be modified for street running.

The biggest difference that comes to my mind is the conducting rail system, whereas trams use now overhead supply although in London there were central area sections that used road conduits, i.e. a slot in the middle of the tramway with collector shoes. The outer areas used a single overhead trolley wire, although there was one section that shared the overhead supply with trolleybuses.

[Deleted]

DLR is most defineatly light rail.

[cetacean]

"Light rail" these days is a euphemism for trams, so the DLR is probably best described as being a heavy rail metro system run using light rail derived vehicles. Trams tend to have minimal signalling and of course run down the streets, whereas the DLR has a full signalling system (possibly the most advanced in the country) and street running would be just about impossible.

[Chris M]

AIUI the DLR signalling system could cope with street running. What is completely incompatible with street running is driverless operation.

The Tyne and Wear Metro is officially light rail although it is borderline heavy rail, with high-level platforms, level crossings, no on-street running and sharing part of its route with the NR heavy rail network. I believe the signalling, even on non-shared sections, is mainline standard two and three aspect. Perhaps the key reason it isn't considered heavy rail is its now unique 1500 volt DC OHLE power supply.

oracle said:

The biggest difference that comes to my mind is the conducting rail system, whereas trams use now overhead supply although in London there were central area sections that used road conduits, i.e. a slot in the middle of the tramway with collector shoes. The outer areas used a single overhead trolley wire, although there was one section that shared the overhead supply with trolleybuses.

There are modern trams, I think in either Bordeaux or Strasbourg, that use a ground-level power supply. The power rail is only live when the section is completely covered by the tram. I don't remember how this works, but I do remember reading somewhere that the system is proving either inefficient or unreliable.

While the distinction between heavy rail and trams is generally clear, light rail blurs into both. I think there is also at least one exception to every defining characteristic - for example the Weymouth Quay branch was heavy rail with on-street running.

[Oracle]

The SR Southampton Docks system used standard gauge, and was an extensive freight, with some passenger, system using steam then from around 1966, diesel traction. In 1940 the docks lines were even used to divert SR main line trains from London to Bournemouth, etc., via Terminus as the tracks around Central had been bombed. The trams were also standard gauge. I have read about tramways that were built to allow standard gauge railway wagons to be towed around the system. The distinction therefore gets very blurred at times.

[Deleted]

cetacean said:

the DLR is probably best described as being a heavy rail metro system run using light rail derived vehicles.

Indeed! It is completely grade-separated from other traffic, has metro-like frequencies and is in an urban environment.

With that it lives up to the definition of a metro/subway/tube/underground according to Urbanrail and Wikipedia.

[Oracle]

LURS used to accept the Metro and the Liverpool system as "underground" systems, in addition to Glasgow's. The proposed but now aborted South Hampshire LRT system was going to be hybrid system with tramway sections (Fareham and Gosport), old heavy rail (Bedenham/Gosport branch) and underground/underwater (tunnels leading to submerged tunnel under Portsmouth Harbour). The DLR uses former heavy rail alignments, elevated and underground/under-water sections but no street running yet. I like to call it a LRT system.

[Deleted]

It's definately not a tram! It is 100% a metro system, as it it self-contained, grade-seperated, and runs at 10min frequencies or better.

There are now so many different types of urban transportation that defining systems can be difficult. In China the term "light-rail" describes elevated "heavy-rail" metros. In the USA "light-rail" often describes partially street running trams. The DLR is however a fairly unique system, certainly not a tram, but not really heavy rail.

The vehicles are light rail vehicles, and some of the infrastructure is only designed for lighter vehicles (steep grades, sharp corners, lightweight structures). However, some of the infrastructure runs along old "heavy rail" alignments. Interestingly the Moscow Metro has in the last few years introduced trains rather similar to the DLR vehicles, some of which run on the existing heavy rail metro system. Photo here (from the excellent urbanrail.net) www.urbanrail.net/eu/mos/img/m4-old-and-new-train1.jpg

The signalling is similar to that found on other driverless/automated metro systems, which include heavy-rail suburban, heavy-rail metro, linear metros, people movers, and a monorail system.

[cetacean]

awkward42 said:

There are modern trams, I think in either Bordeaux or Strasbourg, that use a ground-level power supply. The power rail is only live when the section is completely covered by the tram. I don't remember how this works, but I do remember reading somewhere that the system is proving either inefficient or unreliable.

That wouldn't work for DLR because the third rail is above rail level, and therefore above street level in a street environment. So it'd be impossible for cars to drive across the tracks, which limits you to full grade-separation.

[loughtonsiding]

oracle said:

Isn't it actually light rail, as per the Tyneside Metro? That said, both are often lumped in with say Croydon under "trams", although I believe the overall description might be LRT or Light Rapid Transit. The Metro cars were originally designed so that they could be modified for street running.

And, of course, the original DLR cars were sold to Essen, where they were converted for street running.

What is often forgotten is that prior to sale one unit went to Manchester as part of the development of the Metrolink. It was demonstrated running with overhead collection, near Reddish (at a time when it was envisaged that Reddish depot, made redundant by the closure of the Manchester - Sheffield electrification would become a Metrolink depot). DC traction current was supplied using a BR 25kV EMU on a nearby track as a static transformer/rectifier.

[Deleted]

loughtonsiding said:

And, of course, the original DLR cars were sold to Essen, where they were converted for street running.

Not quite. The ex-DLR cars wern't allowed on the sections of the network that ran on roads due to low braking rates. The ex-DLR cars only operated on the segregated rights of way.

[Deleted]

I think, for a short timescale, the P86 cars did run on BR Metals, during testing stages, the P86 cars were used on the Bury - Altrincham line, which is now part of the Manchest Metrolink

[Deleted]

As part of Project Light Rail a single original DLR cars where used on a freight line in south Manchester, I'll dig out my Metrolink book when Im home to confirm where they did it. Overhead panograph was added to the car. This was before the DLR opened and was to give Manchester a basis to work on for their tram system. The Bury to Victoria and Altrincham to G-Mex was only closed for the adding of overhead wires and platform alternations. The Metrolink was built on the cheap which only now have they actually done something about it.

[Deleted]

It was P86 stock, set 11 that performed the test on the GMPTE track at Debdale Park, in February 1987... This was the first to be sent to Essen in 1991... and no.11 was the set that performed the Royal opening too! This car was indeed fitted with a temporary pantograph...

Indeed, I have only been on the Manchester Metrolink once, and found the stations out to Bury, still clinging to their former BR life...

[Deleted]

You beat me to it Artery. I was on the Altrincham section in april, it needed doing. Be interesting to see how much it changes now with the complete re-newing of the rails.